Earphones placed inside the ear, according to the type of embodiment are divided into two types:
earbuds or plug-in earphones;
in-ear-canalphones or IEMs (In-Ear-Monitors).
Earbuds (inserted)—earphones are inserted into the ear and held there by the resilience force. Earphones of this type do not completely plug the external auditory canal and are placed next to it, directing the sound waves in the direction of the external auditory canal. The disadvantages of this type of earphone may include:                poor sound insulation from ambient noise;        due to the fact that they do not completely cover the external auditory canal, audio quality is significantly degraded;        weakly bound inside the ear if not provided with additional devices to hold it in place.        
But earbuds have certain advantages: they do not irritate the pressure-sensitive surface of the membranous-cartilaginous (front) of the external auditory canal and allow hearing surrounding sounds.
In-ear-canalphones (in various sources, also called vacuum earphones, plugs, ear monitors, in English sources as IEMs)—are worn completely plug the ear canal, providing good insulation against ambient noise.
Compared with earbuds they have a number of tangible advantages:                provide high-quality sound;        in-ear-canalphones—IEM stay in the ear relatively well, since they quite tightly and deeply enter into the external auditory canal.        
The disadvantages of this type of earphones include:                unpleasant and painful sensations during long-term wear, since they strongly pressure on the most sensitive area of the outer ear—the front part of the membranous-cartilaginous portion of the external auditory canal;        ear opening is earphone-plugged, and consequently, it is difficult to outflow from the sebaceous and sulfur glands located in the membranous-cartilaginous portion of the external auditory canal;        due to the relatively good passive noise-isolation, hearing of ambient sounds is difficult;        increases the load on the hearing aid during prolonged listening at high volume levels that can cause hearing loss.        
In some constructive solutions, earbuds are supplied with a directed-into-the ear canal pin with a soft sealing ear cushion. This increases the useful volume of the earphones through the use of internal volume of the ear, not just the ear canal. However, such earphones have all the disadvantages of in-ear-canalphones.
A known custom headset for placement in the ear (US Application Publication No. 2011/0135120 A1), consists of a housing containing a near and remote part, where a remote part has a built-in speaker, and is formed for accommodation in the ear canal of the user. Also, a remote part includes a projection for its seal in the ear canal. This headset has no moving parts, and thus does not give an opportunity to adjust the earpiece in the ear of the user, and does not combine the features of in-ear-canalphones and earbuds.
A known earphone (U.S. Pat. No. 8,265,328) consists of an ear hook, a shaft attached to the end of the ear hook, a housing for an electro-acoustic transducer, a tube allowing the body to move along the shaft, and also includes a cable connected to the electroacoustic transducer and extending inside the ear hook, shaft and housing. This earphone design allows for a minor adjustment of the position of the earphone inside the ear, but only earbuds can be used. Despite the fact that the sliding of the shaft is provided in the tube attached to the earpiece, movement is only possible in the longitudinal axis direction, without rotation. This earphone is rather cumbersome and hook-shaped, which may lead to the engagement of the clothes or wire during an inoperative state. It complicates the use of the earphones in conjunction with other equipment, such as goggles, helmets etc.
A known ear loop for earphone (U.S. Pat. No. 8,320,603), like the previously considered earphones, has a shaft inserted in the ear hook tube that enables adjustment of the earphone inside the ear. This design has the same disadvantages as the previous earphone, and is itself a plug-in with some characteristics of a particular type of earphone, which excludes its transformation into an intra-canal earphone.
A known earphone adapter (U.S. Pat. No. 8,472,660) is intended for earbuds. It comprises a BTE (Behind The Ear) earhook with the option of movable placement of earphone on it, allowing adjustment of earphone. The disadvantages of this adapter is the fact that only earbuds can be used, since the mobility of the earphone on the earhook axis doesn't allow placement of the earphone in an intra-cannel position, i.e., to transform earphone from the earbud into in-ear-canalphones. In addition, when wearing the earhook covers the ear from the outside almost completely, due to which the entire structure is large and has a pronounced hook shape. This adapter has the inherent disadvantages of the two previously considered devices.
A known earbud type of earphone having auricular fastening (U.S. Pat. No. 5,729,615) has the rod rigidly attached to the earphone acoustic elements, where the rod enters into the bushing, a continuation of which is a BTE earhook of earphone. The acoustic element can be rotated relative to the bushing-earhook and vertically lifted or lowered by sliding the rod inside the bushing. The disadvantage is a limited number of adjustments intended for selecting only one relatively comfortable position with the acoustic element in the auricle when using earphones for different people with different anthropometric data. Moreover, an integral fixture of this type of earphone is a massive BTE earhook, increasing the size, complicating form and increasing the number of clinging hook-shaped members in the earphone.
A known device of the earphones with a stabilizer (U.S. Pat. No. 8,374,375) comprises a housing and a flexible member to stabilize the earphone when wearing it by abutting the wall of the ear. The flexible element has two stable positions relative to the housing and respectively earphone can have two positions in the auricle. But in this device change in position of earphone in the ear does not lead to the possibility of its transformation from earbud into in-ear-canalphones.
A known acoustic device with the adaptation for placement in a human ear (U.S. Pat. No. 7,068,803) is an earphone with a spring in the form of a flexible rod, which holds the earphone in the ear of the user, located in a bent state along the wall of the ear. This device provides secure fit of the earphone in the auricle in the only possible position, not allowing adjustment of the earphone or its transformation.
A known hearing aid with a flexible elongate member (U.S. Pat. No. 8,374,367) is made in the form of earbuds, containing a microphone, processor, headset, battery and a flexible elongated portion, one end of which is attached to the housing, and the other is free. When the flexible elongate portion is placed in the user is auricle, the free end is located inside the auricle and outside the ear canal. As with the previous device, a hearing aid is retained in the auricle due to the resilience of the elongated member that enables to secure the unit in the only position.
A known retaining element for micro-earphone for use in hearing aids (U.S. Pat. No. 7,590,255) has in-ear-canalphones provided with elongate resilient member for support on the internal parts of the auricle, where the aggregate resilience of the tissues of the auricle and the elongate member promotes fixation of the earbud in the ear canal, preventing its loss during wear. This element is designed only for hearing aids and also provides for the use of earphone in a simple position, eliminating the possibility of transformation earphone from in-ear-canalphones into earbuds.
A known universal hearing aid (U.S. Pat. No. 7,899,200) also comprises an elongated resilient part to fix the earphone in the user auricle. This unit has the inherent disadvantages of the two previously considered devices.
The general disadvantage of most of the considered earphone devices can also be attributed use of design solutions with ear cushions made of soft material (rubber, foam, rubber foam) for adaptation and fitting of earphone in the ear canal of the user. But soft materials become easily contaminated with dust or earwax, are poorly cleanable and therefore can easily become unhygienic.
Thus, to date there are no in the ear earphones that allow full use of the benefits of design solutions for earbuds and in-ear-canalphones—IEM (In Ear Monitor), depending on current requirements of the user when worn.